<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>克隆</title>
</head>
<body>

<div class="outer">
    <div class="item">
        <button onclick="add(this)">+</button>
        <input type="text">
    </div>
</div>

<script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
<script>

    function add(self) {
     var $clone_obj = $(self).parent().clone();
     $clone_obj.children('button').html('-').attr("onclick","del(this)");
     $('.outer').append($clone_obj)
    }
    function del(self) {
         $(self).parent().remove();
     }
</script>
</body>
</html>